JPS60176995A - Preparation of single crystal - Google Patents

Abstract

PURPOSE:To obtain high-quality single crystal with a few crystal defects and a small amount of impurites, by putting an element of group in a container, controlling a temperarure, growing single crystal from raw material melt while regulating vapor pressure of element of V group in the raw material melt. CONSTITUTION:The seed crystal 6 is supported under the end of the upper shaft 2. The seed crystal 6 is immersed in the raw material melt 5. When the upper shaft 2 is gradually pulled up from the lower shaft 3, the single crystal 7 following the seed crystal 6 is grown. At the lower part of the bottom 1, the element 12 such as As, etc. of group V is laid. In order to control vapor pressure of the element 12 of V group, the temperature in this zone is regulated by the second heater 22. The side wall of the crucible 4 is short, and provided with the partition pipe 16 with a small diameter. The liquid capsuling agent 17 of B2O3 is put in the crucible 4. It in not put in the partition pipe 16. Partial pressure of the element of B group is equilibrated with the atmosphere gas 14 and the raw material melt 5 as a whole. Since the raw material melt 5 is brought into contact with the liquid capsuling agent 17 at the interface 18 of different liquids, so impurities are removed from the raw material melt.

Description

[Detailed description of the invention] C Power Technique Branch The present invention relates to a method for manufacturing a compound semiconductor single crystal.

Compound semiconductor single crystals have a wide range of uses as substrates for integrated circuits, light emitting diodes, laser diodes, and various sensors. Depending on the application, semi-insulating, n-type or p-type single crystals are produced.

Compound semiconductors here refer to IV group compounds.
tl. GaAs, GaP, InP XInA
s, InSb.

There are various combinations of compounds such as GaSb,...

(a) Conventional technology ■-■ When producing compound single crystals, there is a problem in that it is difficult to produce stoichiometric (IJ) thick crystals because the dissociation pressure of group V elements is high.

As a method for producing or growing a compound semiconductor single crystal with a high dissociation pressure, there is a method of growing a crystal in an atmosphere where its vapor pressure is controlled and the pressure of volatile components is brought to an equilibrium state.

This vapor pressure control method is less affected by thermal stress, compositional deviation, etc., and is excellent in terms of crystal stoichiometry (IJ).

Furthermore, a single crystal with a low dislocation density can be obtained.

However, on the other hand, there is still a problem in obtaining highly pure crystals. Furthermore, in an undoped single crystal,
Semi-insulating properties cannot be obtained, resulting in low resistivity. FE
A semi-insulating single crystal is required for use as a substrate for T or the like. In order to increase the resistivity, when producing single crystals using the vapor pressure control method, it is necessary to dope them with impurity elements such as chromium.

The horizontal Bridgman method (HB) belongs to the category of vapor pressure control methods. This is done by placing raw materials in a quartz boat and placing it horizontally, sealing it in a quartz tube, placing a group V element at one end, and gradually changing the temperature distribution in the horizontal method to create a solid-liquid interface. Crystals grow while moving sideways. Vapor pressure is controlled by temperature distribution. In the horizontal type, the ingot shape is semi-cylindrical, and there is a problem that there is a lot of waste when obtaining circular wafers.

On the other hand, there is a compound semiconductor single crystal growth method called the liquid confinement method (LEC method). This involves placing a raw material melt containing raw materials for compounds, impurities, etc. in a crucible, following the raw material melt with a liquid capsule layer, dropping a seed crystal from above, immersing it in the raw material melt, and pulling it up. This method is used to obtain single crystals. High pressure is applied inside the container of the crystal pulling device to suppress the liquid capsule layer and prevent volatilization of group V elements.

The type of liquid capsule depends on the compound raw material melt to be sealed. In the case of GaAs, B2O3 is used as a liquid capsule.

The liquid sealing method has the advantage that semi-insulating single crystals can be produced without doping with impurities.

Furthermore, when B2O3 is used as a sealant, B2O3 has the effect of capturing impurity elements. This has the advantage that the grown crystals have higher purity.

Furthermore, since the liquid sealing method is a vertical growth method, it is possible to obtain an ingot with a circular cross section, and has the advantage that there is little waste when cutting circular wafers.

Another advantage is that the inside of the container is not contaminated with toxic gases such as As.

However, in the liquid sealing method, only the periphery of the crucible is heated with a heater, and the other parts of the container are kept at a relatively low temperature.

Container walls are often water-cooled.

Additionally, B2O3 has a heat insulating effect. For this reason,
The temperature gradient near the solid-liquid interface is large. Therefore, thermal stress occurs during cooling after pulling, and a large number of lattice defects occur. Dislocation density increases. In other words, it is difficult to make good crystals. Furthermore, there is a drawback that the pulled crystal is difficult to achieve stoichiometry. Also, although the lid is covered with a liquid, it is still not possible to completely eliminate the volatilization of Group I elements.

Vertical methods belonging to the vapor pressure control method are also already known. This does not heat only the vicinity of the crucible, but heats the entire container in the vertical direction, making the temperature gradient in the vertical direction gentle. Place group ① elements in a container and balance the vapor pressure.

The temperature distribution in the container is controlled to keep the vapor pressure of the Group Ⅰ element constant at the solid-liquid interface.

Since it is a pulling method, the seed crystal is soaked in the raw material melt and pulled up while rotating relative to each other. The pressure inside the container is not high pressure, but near atmospheric pressure. Since the pressure of the group III element in the raw material melt and the partial pressure of the group III element in the container must be in balance, the upper part of the raw material melt is open and does not come in contact with the group III gas in the container. There is.

The vertical vapor pressure control method is like a vertical version of the horizontal Bridgman method (HB), in which the space above the container is made of GaAs.
In the case of crystal pulling, the temperature is about 600'C.

FIG. 1 is a sectional view of a crystal manufacturing apparatus using the vertical vapor pressure control method.

The container 1 is a container with a sealed structure, and inside there is an upper shaft 2 from above.
However, a lower shaft 3 is provided so that it can rotate and move up and down from below.

A crucible 4 is mounted on the lower shaft 3, and a raw material melt 5 is contained in the crucible 4.

A seed crystal 6 is supported at the lower end of the upper two shafts 2.

After the seed crystal 6 is immersed in the raw material melt 5, the upper shaft 2 is gradually pulled up relative to the lower shaft 3. Then, following the seed crystal 6, the single crystal 7 grows.

Yong! Although the structure of a1 is more complicated, including an opening/closing mechanism, a sealing mechanism, etc., it is shown here in a simplified manner.

” The shaft through hole 68 of the two shafts 2 and the shaft through hole 9 of the lower shaft 3 have a V
Liquid sealant 10.11 to prevent group elements from leaking.
is provided to cover the opening.

This is, for example, B2O3.

In this example, five heaters are used to provide a gentle temperature distribution in the vertical direction. The first heater 21 heats the lowest part of the container 1. This also has the role of melting the liquid sealant 11 before the raw material and sealing the container 1.

The second heater 22 heats the lower part of the container. At the bottom of the container 1, group Ⅰ elements 12 such as As are placed. In order to control the vapor pressure of the group V element 12, the second heater 22 adjusts the temperature in this region within an appropriate range.

The third heater 23 heats and melts the raw material to maintain a liquid state. Further, since the pulled crystal is also heated by the third heater 23, the pulled crystal is not subjected to strong thermal stress. This is because the temperature gradient is alleviated.

The fourth heater 24 heats the top of the container 1.

This involves melting the liquid sealant 1o in the upper shaft through hole 8 as a raw material, and
It is also necessary to melt the group elements prior to heating.

While appropriately setting and readjusting the power of the first to fourth heaters, make sure that the temperature gradient does not become steep in the container 1,
At the gas-liquid interface 13, the partial pressures of group Ⅰ elements between the gas and the liquid are balanced. If the partial pressure of the group (1) element at the gas-liquid interface 13 is constant and at a certain appropriate value, a stoichiometric single crystal can be pulled.

Such a previously proposed vertical vapor pressure controlled pulling method yields a single crystal with excellent stoichiometry and a low dislocation density.

(1) Prior art and its problems In the vertical vapor pressure control method, however, the liquid capsule does not cover the melt, so the impurity trapping effect of the liquid capsule cannot be expected.

It is assumed that B2O3 is placed on top of the raw material melt 5 in order to reduce impurities by the action of a liquid capsule. Then,
Although it has the effect of absorbing impurities, the liquid capsule blocks the raw material melt 5 and the atmospheric gas 14. For this reason, the vapor pressure of the group (Ⅰ) element is not balanced between the gas and the liquid, making it impossible to control the vapor pressure.

Although it is possible to make the liquid capsule B2O3 thinner, it is still not sufficient. Since the exchange between the liquid and the gas of group (1) elements occurs, an equilibrium state is reached, so if B2q is present, a complete equilibrium state will not be reached.

(:C) Object of the Invention The present invention falls under the category of vapor pressure control method, and provides a method for producing a compound semiconductor single crystal that also effectively takes advantage of the impurity trapping effect of a liquid capsule.

K) Method of the present invention In order to achieve both the advantages of the vapor pressure control method and the impurity capture effect of the liquid capsule, a part of the surface of the raw material melt 5 is covered with a liquid encapsulant, and the remaining part of the surface is is in contact with atmospheric gas. The raw material melt 5 is partitioned by placing partition pipes in the liquid. It is arbitrary which part of the surface 14 of the raw material melt 5 is partitioned.

FIG. 2 is an enlarged sectional view of only the vicinity of the crucible to illustrate the method of the present invention. Illustrations of the container 1 and the heater are omitted.

A short partition pipe 16 with a small diameter is attached to the side wall of the crucible 4. A B2O3 liquid capsule 17 is placed in the crucible 4. Do not enter the partition pipe 16. The surface 15 of the raw material melt is in contact with the atmospheric gas 14 inside the partition pipe 16 and in contact with the liquid capsule 17 outside the partition pipe 16 .

The part of the surface 5 that comes into contact with the atmospheric gas 14 is called a gas-liquid interface 13, and the part that comes into contact with the liquid capsule 17 is called a different liquid interface 18.
I will call it here.

At the gas-liquid interface 13, since it comes into contact with the atmospheric gas, the partial pressure of the group V element is balanced between the melt 5 and the atmospheric gas 14. The melt 5 is made to have a uniform component ratio and temperature by convection. In the end, the partial pressure of group Ⅰ elements is 14
This results in equilibrium throughout the raw material melt 5.

Since the raw material melt 5 and the liquid capsule 17 come into contact at the different liquid interface 18, impurities are removed from the raw material melt.

The area ratio and distribution of the gas-liquid interface 13 and the different liquid interface 18 are arbitrary.

FIGS. 3 and 4 are cross-sectional views (a
) and a plan view (b).

In the example shown in FIG. 3, the partition pipe 16 is provided so as to be concentric with the crucible. A liquid capsule 17 is contained inside the partition pipe 16, and the outside of the partition pipe 16 is exposed to the atmospheric gas 14. Although the means for fixing the partition tube 16 is not shown, it may be erected on the bottom of the crucible 4 by attaching legs. It can also be fixed to the side wall of the crucible.

In this example, the single crystal is pulled through the liquid capsule 17.

The surface 15 of the raw material melt 5 has a different liquid interface 18 on the inside and a gas-liquid interface 13 on the outside.

In the example shown in FIG. 4, on the contrary, the liquid capsule 17 is placed on the outside of the partition pipe 16, and the inside is open. The raw material melt contacts the atmospheric gas 14 inside the partition pipe 16 .

(Force) Effects (1) Since it is a vertical steam pressure control method, stoichiometric)
IJ footer compound semiconductor single crystals can be manufactured. Compositional deviation is small, and compositional deviation can be controlled arbitrarily.

(2) Since the temperature gradient in the vertical direction is small, a high quality single crystal with few crystal defects can be obtained.

(3) Since a part of the surface of the raw material melt is covered with a liquid capsule, impurities are removed thereby. Single crystals with few impurities can be made. In particular, a semi-insulating single crystal can be obtained even if it is undoped.

(g) Applications This invention is widely used for growing compound semiconductor single crystals containing group V elements with high dissociation pressure. For example, GaP, I
nPXGaAs, InAs, etc.

(ri) Implementation example An InAs single crystal was manufactured by the method of the present invention.

The Ton crystal pulling device has a structure as shown in FIG. 1, and the inside of the crucible 4 is arranged as shown in FIG. container 1,
The crucible 4 and the partition tube 16 were made of Noseiro Litique boron nitride (PBN).

Crystal growth is performed near the melting point of InAs, 943°C.

The As pressure in the container is the dissociation pressure of InAs (0.33 atm
), and the temperature near the bottom was controlled using the second heater 22.

The crystal rotation speed and the crucible rotation speed are 1 to 1-OrF', and the growth rate is 3 to IQ+++a+/h. B2O3
was made into a liquid capsule. The thickness was 5 to 20 mm.

The obtained crystal has a diameter of 50 mm and a length of 15.0'W.
ff, and the dislocation density was 1000/z or less. There was no difference in composition.

A semi-insulating crystal with few impurities and a resistance value of 10 3 to 10 9 Ω (7) was obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a known vapor pressure controlled single crystal manufacturing apparatus. FIG. 2 is a longitudinal sectional view of an apparatus near a crucible for carrying out the single crystal manufacturing method of the present invention. FIG. 3 is a diagram of a crucible to show another embodiment, (a)
is a vertical sectional view, and (b) is a plan view. FIG. 4 is a diagram of a crucible for showing other embodiments.
(a) is a longitudinal sectional view, and (b) is a plan view. 1... Container 2... Upper axis 3... Lower axis 4... Crucible 5... Raw material melt 6... Yuzu crystal 7...・Single crystal 8.9 ... Axial hole 10.11 ... Liquid sealant 12 ... ■Group element 13 ... Gas-liquid interface 14 - Atmospheric gas 15 ... Raw material Surface of melt 16 Partition pipe 17 ... Liquid capsule 18 ... Different liquid interfaces 21 to 24 ... Heater inventor: 1) Hiroji Masami Ryuumi Patent applicant: Sumitomo Electric Industries, Ltd. Co., Ltd. Figure 2 Figure 3 Figure 15 (a) Figure 4

Claims (1)

[Claims] A sealed container 1, a plurality of heaters 21, 22, . 3 and
A raw material for a compound semiconductor is put into the crucible 4 of the single crystal manufacturing apparatus, which is made up of a crucible 4 supported by a lower shaft 3, and is melted by a heater to form a raw material melt 5, and in the container 1, group Ⅰ elements constituting the compound semiconductor are placed. A partition pipe 16 is placed in the crucible 4 to divide the 5° surface of the raw material melt into two parts, one of which is covered with the liquid capsule 17 and the rest of the surface is in contact with the atmospheric gas 14. Production of a single crystal characterized by growing a single crystal 7 from the raw material melt 5 while controlling the vapor pressure of the group V element in the raw material melt 5 by adjusting the element 12 and the temperature inside the container. Method.